Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$87.65	10.424%	$96.7866	$96.79	$96.80	$96.80
Purchase #2	$247.79	5.440%	$261.2698	$261.27	$261.25	$261.30
Purchase #3	$86.66	13.665%	$98.5021	$98.50	$98.50	$98.50
Purchase #4	$36.76	7.753%	$39.61	$39.61	$39.60	$39.60
Purchase #5	$210.27	8.215%	$227.5437	$227.54	$227.55	$227.50
Purchase #6	$140.71	7.394%	$151.1141	$151.11	$151.10	$151.10
Purchase #7	$121.33	9.186%	$132.4754	$132.48	$132.50	$132.50
7 purchase totals =	$931.17		$1,007.3017	$1,007.30	$1,007.30	$1,007.30